Accelerated degradation tests (ADTs) for the H-2/air single cell are carried out at 65 degrees C and ambient pressure by cycling the cell between 0 and 200 mA cm(-2) up to 6000 cycles. Membrane electrode assemblies (MEAs) are prepared using the Nation 212 membrane and the carbon supported platinum as an anode catalyst, as well as the carbon supported Ru85Se15 as a cathode catalyst prepared with five selected Nation contents and Ru loads to represent the optimized (33% Nation and 0.27 mg Ru cm(-2)), overloaded (43% Nation and 0.61 mg Ru cm(-2)) and underloaded (20% Nation and 0.14 mg Ru cm(-2)) conditions. The lowest cell performance loss of 44% in terms of peak power density is achieved with 33% Nation and 0.27 mg Ru cm(-2). Very severe losses of 80% and 82% are found for 20% and 43% Nation contents, respectively, while relatively moderate losses of 57% and 64% for 0.14 and 0.61 mg Ru cm(-2), respectively. Dissolution and migration of Se/Ru and corrosion of carbon support from the catalyst, together with the shrinkage and release of sulfonic acid from the membrane are identified and correlated to decayed cell performances. (C) 2012 Elsevier B.V. All rights reserved.